Method and apparatus for treating fiber



Dec. 20

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^ A. F. RICHTER ET AL METHOD AND APPARATUS FOR TREATING FIBER FiledJuly19. 1926 2 SheetsfSheet 2 HccuMuLnroR TANK Hom SUPPLY LINE ToDIGEsTERs.

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l/steam1ng process of cooking is employed,

Patented Dec. 20, 1927.

UNITEDYA STATES l1.653.416 .PATENT OFFICE..

.AU'GUST F. RICHTER, 'OF WATERTOWN, AND FRANK A. AUGSBURY, OFOGDENSBURG',

NEW YORK, ASSIGNORS T0 STEBBINS ENGINEERING AND MANUFACTURING COI- uPANY, OF WATERTOWN, NEW YORK, A CORPORATION OF NEW YORK.

METHOD AND APPARATUS ron TBEATING FIBER..

is discharged from the digester during'- treatment.' 4

In general, where the quick cook or direct Ythe relief gases driven oliffrom the liquor in the digesters during the cooking process, are passedthrough relief gas coolers and after being cooled, this gas is passedinto the bottom of the acid storage tank or it isv sometimes passed intothe bottom of an absorption or recovery tower, the raw acid beingsprayed into the top of the recovery tower and the gas, (in the case ofthe sulphite process, this is SO2 gas) iowing upward under pressuremeets the down coming acid and is absorbed. Heretofore, it-

has been necessary to cool the sulphur dioxide gas in order that itmight be absorbed by the'liquor. Due to this cooling, the acid, whenpumped into the digester, requires an excess of steam to bring thetemperature and pressure up in the digester.

It is also well known that quick cooks at high temperature have adestructive eiect upon the cellulose in the wood, and low temperaturecooks, (which necessarily take a longer time) do not have as destructiveeffect upon the cellulose. Further, when cooking/is carried on at acomparatively low temperature, the yield of pure cellulose is higher.Our method and apparatus are applicable to both quick cook and slow cooksystems.

In our process, no cooling of the gas from the digesters is required, asthe gas is absorbed under pressure, thereby. conservingA thev heat unitswith the 'direct result that there is a considerable saving of steamduring the cooking process.

' Briey, one phase of the present invention consists in passing the hothigh andlow pressure relief `fases from the digesters into anaccumulator tank where the gases are absulaton tion when it is appliedto the fibrous material in the digester. l

The invention is illustrated in the accompanying drawings, in which,

Fig. 1 is a diagrammaticview of one a paratus forming the subject matterof tliie present invention.

Fig. 2 is a similar view of a modification.

Fig. 3 is a vertical sectional view of a detail taken on line 3-3 ofFig. 1.

In general, the apparatus consists of onev or more digesters, 1, 2, and3,' an acid accumulator 4, and one or more-acid storage tanks 5 and 6.`'Although three digesters have been illustrated in Fig. 1, theapplication can be employed'with any number vof digesters, orwith anynumber of acid storage tanks. In -this connection, it may be stated thatitis general practice to emplo three acid tanks if three digesters areuse' but only two acid storage tanks are used with the presentinvention, and these are combined with the acid accumulator 4.

The digesters employed are of the standard steel shell type now incommon use, and' in the sulphite process these digesters are lined withan acid resisting metal. Also the acid storage tanks 5 and 6 maybe ofsteel or concrete with an acid resisting lining, or they may be made ofwood. These pieces of apparatus are all in common 'use inrnany mills nowoperating. The acid accumulator is not now in use, but it may be of thesaine general construction as each of the digesters and must be providedwith an acid proof lining. We have shown the accumulator as arrangedvertically, but it may be arranged horizontally and be as equallyeffective, provided that the same relative positions o f the inlet andoutlet pipes are maintained. This accumulator may be of any shape founddesirable. The digesters and acid accumulator may or may not be coveredwith a heat in- As these pieces of apparatus are lined, the lining actsas an insulator, but additional insulation may -be provided ifnecessary.

` process may be made in any known way and pumped from the acid systemto the storage tanks by way of the pipe 7. p

The digesters are cooked in rotation, which is now common practice, andthe wood chips or other fibrous material are introduced into thedigesters from an overhead bin or chip conveyor (not shown) throughsleeves 8 having covers 9. The liquid acid is forcedy into the bottom ofthe digester through pipe 10, either by an acid pump 11, or by applyingsteam pressure to the top of the accumulator 4, and driving the acidfrom the tank 4 through the pipe 12 and into the pipe 1Q. At this point,it will be noted that the pipe 10 is connected to the digesters bybranch pipes 13, 14, and 15, each having a control valve 16, 17 and 18.The pipe 12 is also provided with a control valve 19, and the pump 11 isconnected to the bottom of the accumulator tank by a pipe 20 having acontrol valve 21.

rIf the acid from the accumulator 4 is to be forced into the digester by`the pump 11, the valve 19 is closed and the valve 21 is opened, but ,ifsteam pressure is used instead of the pump, then the valve 21 is closedand the valve 19 is opened.

This method of forcing the acid into the digesters by pressure appliedto the accumulator is new, and its advantages are that this steampressure further heats up the acid, thereby assuring a betterpenetration of the acid into the chips before the cooking process isstarted. One of the desired results is thereby accomplished, as it isalways advantageous to have the acid as hot as possible in order tosecure quick penetration of the acid into the wood chips. The quickerthis penetration is accomplished without carbonizing the chips, thebetter will be the pulp produced. besides" saving. time and investment.The pipe for introducing steam into the accumulator tank is shown at 22and it is provided With a control valve 23.

During the cooking process, the gas from y the digesters is permitted todischarge into relief gas lines. In accordance with the presentinvention there are two rehef lines provided; one a high' pressurerelief gas line" 24, and the other a low pressure line 25. The pipe 24is connected to each digester by two branches 26, each having a controlvalve 27 therein. The low pressure pipe 25 is connected to each digesterby two branches 28 each having a manually controlled valve 29 land anautomatic check valve 30. Heretc 10W pressure line 25, which isconnected to the upper portion of the accumulator tank at the point 31.As the digesters are worked in rotation, there is almost a. contant iiowof low pressure gas into the accumulator -1 when three o1' moredigesters are employed. It three or more digesters are used, the coldacid from the storage tankNo. 5 is continuously forced by the pump 32through pipe and sprayed into the top of the accumulator 4. This coldliquid showering in the tank 4 condenses and absorbs the hot incomingrelief gas from the pipe 25. If only one or two digesters are connectedup to the acid accumulator.l the pumping of acid is necessarilyintermittent. Y

During the time that low pressure SO2 gas is being relieved from some ofthe digcsters into the top of the accumulator 4, SO2 gas at highpressure is being relieved into the high pressure lineA 24, and carriedinto the bottom of the accumulator/4 from the other digesters. This highpressure relief gas'passes into the tank 4 at the point 34 and bubblesup through the acid in the accumulator, and is thereby absorbed into theacid liquor, in this way building up the strength of the acid in theaccumulator. A three way plug cock 35 is provided in the high pressureline 24 and is connected to the upper portion of the accumulator by ashort pip-c 36, so that gas from thehigh pressure line can be admittedinto thetop ofthe accumulator, when the pressure inthe latter drops to apoint below that caused by the static head of the acid liquor in theaccumulator. This is particularly necessaryl when the last cook is beingfinished preparatory to a shut down, and also at certain periods whenthe digesters get out of step from their regular sequence of operation.l

We will now assume that digesters Nos. 1 and 2 are already cooking, andNo. 1 digester has been on for eight hours, and No. 2 for four hours.No. 3 digester has just been illedwith chips and acid, and the cookingprocess just started. At this time, digesters 1 and 2 Will both berelieving into the high pressure gas relief line 24. This gas passinginto the bottom of the accumulator and bubbling up through Vthe acid andbeing absorbed thereby. Due to this, the acid liquor in the accumulator4 is heated up so that this heated liquor may be forced by the pump 11or by steam introduced through the pipe 22, from the accumulator 4 into-the lower end of the digester No. 3. As soon as the cook is started indigester No. 3, the valve to the low pressure relief gas'line is openedvand the gas is driven out by thc application ofsteam tothis digester.In ,thc event that the gaspressureon the top of the acid in theaccumulator'is higher than the pressure in the digester` the check.valve 30 will close and prevent the flow of 'gas from lll) lli

Lesa-11e the accumulator back into the digester, but as. soon 'as thepressure in No. 3 digester is higher than that in the accumulator, thegas will flow from No. 3 digester into the top of the accumulator whereit will be absorbed by the acid which is being pumped and sprayed intothe accumulator from the storage tank by way of pipe 33. After the coldacid is pumped from the storage tank 5 into the accumulator, it willcondense and absorb the gas in theaccumulaton Any gas that is notabsorbed during this process will pass through the vent line 37, intothe lower end of one or more of the digesters, or it may be passedthrough the pipe 38 into the lowerportion of the storage tank 5 where itwill be absorbed by the acid liquor in this tank. Suitable valves 39 and40 are provided in these pipes to control the flow. A vent line 41 isalso provided for the storage tanks 5 and 6, this vent line being led tothe acid system (not shown), so that the gas which Aforms on the top oftheracid storage tanks,

will be absorbed in the acid making system, thus preventing the loss ofgas.

As soon as No. 3 digester has been brought up to approximately poundspressure, the valves 29 of that digester are closed, and the valves 27of the same digester are opened, so that the high pressure gas isreleased into the line 24. At this time, the digester No.' 3

will have been cooked about four hours, and

No. 1 digester will be ready to be dropped in ressure. As soon as'theressure in No. 1l digester drops, the'valves 2 of that digesf. ter willbe closed and. the valves 29 of the same digester will be opened, topermit the low pressure gas to travel to the accumulator. The abovedisclosure is based on a total ,cycle from fill 'to fill ofapproximately 16 the accumulator, so that this liquor is 1n preheatedcondition before it enters a digester which is about to be started. Thesteam for cooking isi'ntroduced to the digesters by the well known meansnow generally employed. Y

y' In the modification illustrated in F ig. 2 we have illustrated twoaccumulators, and

i 51, hooked up with pressure or thermostatic control devices 52 and53,v (these are both standard equi ment and can be purchased on themarket so that the relief gases from.

the digesters, and liquor from the acid stor- I age tanks 54 and 55 areautomatically changed, from one accumulator-to the other.-

That is, when one accumulator is up to a predetermined pressure, thegases and lliquor are automatically switched over to the otheraccumulator, leaving the first ready to discharge its contents into adigester whenever desired, this being automatically accomplished byopening the acid supply line leading into the digester. As the pressureand temperature in the irst accumulator drops, due to emptying itscontents and filling the digester, steam is automatically admitted tothe top of this accumulator, maintaining the proper 'pressure therein toforce the acid to the digester which is being filled. During thisperiod, the low pressure vent line at the top of the digester vundergoing filling, is opened. In this modification, 24a designates thehigh pressure 4relief gas line, which is provided with av control valve24". Just be. low the valve 24", the pipe is branched at 24C, and' thesebranches are connected to the upper portion of the accumulator tanks.The pipe extends downwardly and is connected by valved branches 24d tothe lower portions of the accumulator tanks. Thelow pressure relief gasline is 'designated 25, and is connected by branches 25b to the upperportion `of each accumulator tank.

The acid is supplied Vto the accumula-tor tanks by means of a pump 56which forces the acid liquor -through a pipe 57 having `valved branches58 connected to the l,tops of the accumulator tanks.

The acid is 'fed from' the accumulator tanksl to the digesters by meansof a pipe .59'

which is connected by valved branches 60 `to the lower ends of theaccumulator tanks.

Steam is supplied to the accumulator tanks "by means of a pipe 61 havingvalved'branches losA 62 connected to the tops of the accumulator tanks.l A

As soo`n as the digester has been from thefrst acid accumulator, thevalve in the acid supply line to the digester is closed ,and the steamatthe top of the accumulator is shut oil by closing the valve in thebranch 62. This causes the temperature and pressure Ain this particularaccumulator to drop, and as soon as it has dropped suiiciently, the

automatic pressure or thermostatic controldevices 52, 53, automaticallychanges the valves, so that this accumulator-will again fill withacidfrom the storage tanks 54,55,

whilethe gas from the digesters is being recommonly called blow pits.`thus partially washed, and therefore does on the high pressure reliefline is automatically opened. Such automatic regulation of valves iswell known, and no specific means Afor accomplishing this need beillustrated.

Manual auxiliary control in this instance is also provided, so thatdigesters can be handled in this 'manner in case the automatic featureshould for any reason fail to function. Occasionally, a check valve oran automatically controlled valve will stick, and under suchcircumstances, the digesters'may be controlled by manual valves, that isthe reason why we prefer to use two valved branches 26, and two valvedbranches 28 for each digester. I.

Under our method of producing cellulose pulp, and handling digesters, wealso prefer to provide a strainer at the bottom ofeach digester, so thatwhen the cook is finished, the liquor is drawn of at the bottom of thedigester through this strainer. In Figs. 1 and 3 we have illustratedsuch strainers and have designated the same 70. The strainer holds backfthe cooked pulp and allows the liquor to bledrained out and sent to thesewer "or else to thewaste liquor fuel recovery system, or wherever itis required. During the time the liquor is drained out of the digester,hot water is being pumped into the top through the line 71 which isprovidedwith valved branches 72. This water. drain.- ing down throughthh pulp, partially washes same, so that when thewdumping valve, (notshown) is opened, the pulp is allowed to go into the drain pits (notshown), or what are Tho pulp is not contain much acid. As soon as thepulp has been partially washed in the digester,

this dumping valve or blow-od valve previ-` ously mentioned, is openedand the hot water entering the top of the digester will wash thecontents of the digester Vout of the same and into the blow or drainingpits. Due to this operation the fibers do not explode asis the case whenthe contents of the digester are blown out under pressure, therefore theibersare not injured andthe pulp produced is of a better qualitythanthat produced when the liquor is not drained out, and the liquor'and pulp are blown out into the blow pit by pressure applied to. theinterior of the digester. We also prefer to arrange a hot water wash outline and that is commonly called the blow off elbow, so

that .this hot water comes in on a line par.

allel to the center line of the dischargepipe leading to the pits,thereby having a siphon effect in removing the contents' of thedigester. In our method, the contents lof the digester are handled muchmore gently than under the old practice, both as regards the cookingandthe emptying, which produces a higher grade of pulp as abovementioned.

Our method of using the acid accumulator is applicable to both quick andslow cooks, as also 1s the method of dumping or emptying the dige ters,it only being necessary to so .and pressure, is accomplished lin thesame manner now 4generally employed in quick cook systems. Theadvantages of our method, however, are that the heatsunits in thereliefgas and liquor, are conserved and the pulp produced is of a higher andpurer uality.

Although we have not s own it, aside relief valve for removing part ofthe liquor during the cooking process is also provided. This reliefdischarges the liquor removed from the digester during ythe cookingproc-` ess, back into the acid storage tanks, and this liquor is mixedwith the\raw liquor from the acid system, as is standard practice atthis time.

From the foregoing, it is believed that the construction and operationof our apparatus, and the novel steps of our method, may be clearlyunderstood, and it will be apparent to those skilled in the art thatchanges may be made in the details disclosed, without'departing from thespirit of the-invention as expressed in the claims. v

`What we claim and desire to secure by Letters Patent is v 1. A methodof treating fibrous material consisting in placing the same in .closedchambers, digesting the material in one of said chambers with acid underheat and pressure, liberating low pressure gas from,

liquor under pressure to absorb the gas and v heat the liquor, andintroducing this heated liquor into the second chamber for digesting thematerial in that chamber.

2. A method of treatin fibrous material consisting in feeding acidliquor into the Aupper portion of an accumulator chamber, placin thefibrous material in first and second digester chambers, digesting themate-` rial in the first chamber with acid under heat and pressure,releasing low pressure gas from the first digester chamber for apredetermined period of time and feeding the same into the upper portionof the accumulator chamber, subsequently releasing high pressure gasfrom the first digester'chamber and feeding the same into the lowerportion .gases in the accumulator chamber wit the of the accumulatorchamber, contactin said acid liquor to absorb the gas and heat theliquor, and feeding this heated liquor into the second digester chamberand contacting the same with the fibrous-material therein for digestionpurposes.

3. In a method of treating fibrous material, digesting the material withacid in av z,consisting in placing the lmaterial in first and seconddigester chambers, digesting the material in one of said chambers withacid under heat and pressure, passing gas from thel first chamber to anaccumulator chamber, contacting the as in the accumulator chamber withacid liquor to absorb the gas and heat the liquor, and introducing steaminto the accumulator chamberV for heating liquor, and' heating the liuor by the gas enriched liquor and for forcing the. same in this heatedcondition `into contact with the material in the second chamber.

5. In an apparatus for treating fibrous material, aV digester and anaccumulator, a high pressure relief gas line connecting the digestertothe accumulator,'a low pressure re ief gas line connecting the digesterto the accumulator, valves arranged in said lines, means for feedin acidliquor Linto the accumulator for absorlingthe gas by the the gas andmeans for feeding t e gas enric ed heated liquor .from the accumulatorinto the digester.

or the other, means 'for feeding acidllquor len into the accumulatorforabsorbing the-gas and heating the liquor, and means for' feed-f ingthis gas enriched heated liquor to Vthedi ester.

An apparatus for treating fibrous material comprising a digester and anaccumulator, said accumulator, means for feedlng relief as for thedigester into the accumulator or contacting t e gas with the liquor, aconduit connecting the accumulator to the lowerl ortion of the digester,and means for feedlng aqueous steam from an outside source into t eupper portion of the accumulator Vhigh pressure relief tion o .jA'napparatus for. treatingbrous maf. terial` comprising a digester and anaccumumeans for feeding acid liquor into for forcing the liquor through,the conduit into the dlgester. A

8. An apparatus for treating fibrous material com rising a digester, anaccumulator, an aci storage tank, means for forcing and feeding acid.liquor from the storage Y tank to the accumulator'tank, a conduit forfeeding acid liquor from the accumulator to the digester, a highpressure relief gas line connecting `the upper portion of the digesterto the lower portion of the accumulator, a low pressure relief gas lineconnecting the 'upper portion of the digester to the upper portion ofthe accumulator, and means for forcing acid from the accumulator to saiddigester. .f

9. An apparatus-as-,claimed in claim 8 including a vent as pipe forleading vgas from the accumu ator to the storage tank. 10. An apparatusas'claimed in claim 8, including a by-pass pipe for connecting the I asline to the upper portion of the accumu ator,:.and a valve forcontrolling the passage of high .pressure relief gas to either the upperor lower porthe accumulator.

1l. A method of treating fibrous material, consistin in placing thematerial in a chamber, plac g acid liquor in a tank, introducing aqueoussteam under pressure from an outside source into said tank for preheatinsaid `acid liquor, and utilizing the pressure ofthe steam for forcingthe preheated acid liquor fromthe tank'v into said chamber and intocontact with the material in the chamber.

its lower end, a -screen in said outlet, means for introducing acidliquor into said outlet beneath'the screen, and means for introducinghot ,liquid into the upper end of the digester for washing acid out ofthe materialin the digester and through-said screen. 13. A method oftreating fibrous material, consisting in placing a raw material in firstand second digester chambers, digesting the material inthe first chamberwith acid under heat and pressure,-`releasing low pressure gas from thefirst vchamber for a predetermined period 'of time, subsequentlyreleasing high` pressure gas from the first chamber for a predeterminedperiod of time, contacting said gases with acid li uor under pressure toabsorb the as and eat the liquor, and contacting the eated li uor withthe fibrous material 1n the second igester chamber for digestingpurposes.

14. A method oftreating fibrous materlal, consisting in feeding acidliquor into the upper portion of an accumulator chamber, placing thefibrous' material in a dlgester chamber, di stin the material in thechamber with acid un er heat and-pressure, releasing low pressure gasfrom the digester chamber for a predetermined period of time and feedingthe same into the upper portion of the accumulator chamber, releasing atanother period of time, high pressure gas fromV the digester chamber andyfeeding the same into the lower portion of the accumulator chamber,contacting said gases in the accumulator chamber with acid liquor underpressure to absorb the gas and heat the liquor, and contacting thisheated liquor with fibrous material for digestion purposes. 15. In amethod of treating fibrous material, digesting the material with achemical solvent in a number of closed chambers under heat and pressure,releasing gas from the chambers and contacting the same in heatedcondition with pre-conditioned chemical solvent in an accumulatorchamber under superatmospheric pressure to absorb the gas and heatthe-solvent, releasing gas from one .of said chambers and contacting thesame with fresh chemical solvent of 'a supply chamber arranged at alower elevation than the top of 'the accumulator chamber, pumpingpre-conditioned chemical solvent from the supply chamber into theaccumulator chamber, and feeding the chemical solvent rom thelaccumulator chamber, into one of said closed chambers. v

16. In -a liber treating method, digesting the fiber in a pluralityi ofclosed chambers under superatmospheric pressure with heated acid liquor,lreleasing acid ygas from said closed chambers and passing the same intoa closed. accumulator chamber, contacting said gas"in the accumulatorchamber with pre-conditioned acid liquor, releasing acid gas from one ofsaid chambers and contacting the same with fresh acid liquor of astorage tank arranged at a lower elevation than the top of theaccumulator chamber to pre-condition said fresh acid liquor, feeding thefresh acid liquor thus pre-conditioned from the storage tank into theaccumulatorchamber, and passing the acid liquor from the accumulatorchamber into one of said closed chambers. Y

17. In a liber treating method, digesting the liber in a closed chamberwith a heated chemical solvent, releasing gas from said closed chamberand passing the same in its heated condition into. an accumulatorchamtained in the iirst chamber, and utilizing ber, feeding freshchemical solvent from a supply tank arranged at a lower elevation thanthe top of the accumulator chamber,

into the accumulator chamber, and contactrial. digesting the materialwith a chemical solvent in a closed chamber, releasing high pressure gasfrom said closed chamber foi` a period of time, and passing the same inheated condition into a second chamber, contacting said gas in thelatter chamber with chemical solvent, releasing low pressure gas fromsaid first Aclosed chamber for another period of time, and contactinsaid low pressure gas in heated condition with fresh chemical solvent,and feeding the solvent after it has been heated by said contact into a'closedchamber for digesting fibrous material.

'19. A method of treating fibrous material, consisting in placing thesame in closed chambers, digesting the material in one of said chamberswith acid under heat and pressure, liberating high pressure gas from thelast mentioned chamber for a period of.

time, liberating low pressure gas from the last-mentioned chamber for asubsequent period of time, contacting these gases with acid liquor underressure to absorb the gas and heat the liquor, introducing this heatedliquor into the secondV chamber for digesting the material in thatchamber, discharging the acid from the rst chamber while retaining thematerial therein, washing the material with liquid while it is conaliquid to wash the material out of the first chamber.

Executed June 16th, 1926.

AUGUST F. RICHTER.

FRANK A. AUGSBURY.

